Medical Masks Versus N95 Respirators for Preventing COVID-19 Among Health Care Workers
Authors: Christine Laine, Christina C. Wee, Stephanie Chang, Deborah Cotton, Vineet Chopra, Sankey V. Williams, Yu-Xiao Yang, Eliseo Guallar, Eric A. Ross
Journal: Annals of Internal Medicine (2023)

LettersJuly 2023Medical Masks Versus N95 Respirators for Preventing COVID-19 Among Health Care WorkersFREEChristine Laine, MD, MPH, Christina C. Wee, MD, MPH, Stephanie Chang, MD, MPH, Deborah Cotton, MD, MPH, MA, Vineet Chopra, MBBS, MD, MSc, Sankey V. Williams, MD, Yu-Xiao Yang, MD, MSCE, Eliseo Guallar, MD, MPH, DrPH, Eric A. Ross, PhDChristine Laine, MD, MPHEditor in Chief, Annals of Internal Medicine Search for more papers by this author, Christina C. Wee, MD, MPHSenior Deputy Editor, Annals of Internal Medicine Search for more papers by this author, Stephanie Chang, MD, MPHDeputy Editor, Annals of Internal Medicine Search for more papers by this author, Deborah Cotton, MD, MPH, MADeputy Editor, Annals of Internal Medicine Search for more papers by this author, Vineet Chopra, MBBS, MD, MScDeputy Editor, Annals of Internal Medicine Search for more papers by this author, Sankey V. Williams, MDDeputy Editor, Annals of Internal Medicine Search for more papers by this author, Yu-Xiao Yang, MD, MSCEDeputy Editor, Annals of Internal Medicine Search for more papers by this author, Eliseo Guallar, MD, MPH, DrPHDeputy Editor, Statistics, Annals of Internal Medicine Search for more papers by this author, Eric A. Ross, PhDAssociate Editor, Statistics, Annals of Internal Medicine Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/L23-0074 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail IN RESPONSE: It is unsurprising that a trial comparing medical masks with N95 respirators for health care workers generated strong response given the controversial, emotionally laden topic that masking has become. The editors recognize the trial's limitations, but we disagree with readers who call for retraction.First, we emphasize that the results were not “null” as some of the comments and media coverage incorrectly suggest. The article and accompanying editorial state that the results are inconclusive; the noninferiority margin was larger than many would consider important; and the substantial heterogeneity across locales and time of enrollment suggest that such factors as circulating variant, vaccination rates and type, and prevalence of prior infection influence the effectiveness of different masking policies for health care workers. We chose to publish the article because even inconclusive trials contribute evidence toward answering important questions.Several comments suggest that equipoise was lacking. Yet, a strong indicator of equipoise is that, at the time of the study, 2 authoritative bodies—the World Health Organization and Centers for Disease Control and Prevention—recommended different mask types for health care workers caring for persons with COVID-19. Others fault the trial for not including a “no-mask” control group; however, the inclusion of a no-mask group would have been unethical, because masking in the health care setting was standard practice at the time of the trial.Laboratory studies provide evidence of the physical properties of different mask types but not on the clinical effectiveness of different masking policies. As several readers note, perfect mask adherence is unlikely in any health care setting. The trial provides evidence of the effectiveness of 2 real-world masking policies—and in the real world, a mechanism for variable effectiveness of one mask type over another could be that one mask type, even if more effective at blocking aerosols in an experimental setting, may be more uncomfortable than another, leading to worse adherence.The comments that fault the trial because of a lack of universal masking missed the following statement in the Methods section: “The intervention included universal masking, which was the policy implemented at each site. This refers to the use of a mask when in the health care facility for all activities, whether patient related or not, including in workrooms, meetings, and treating persons that were not suspected or known to be positive for COVID-19.”Some express concerns about the motivation for the addition of study sites. However, the need to expand the trial beyond Canada was driven by mandates that health care workers in Canada receive a highly effective COVID-19 vaccine. The addition of sites without such vaccine mandates enabled the investigators to study participants who had not received a highly effective vaccine, thus isolating the relative benefit of masking methods. Modification of trial protocols is not optimal, but the need to do so was inevitable in many trials conducted as the pandemic evolved. These changes were noted in the article and Supplement but should also be noted in the registry. We have asked the investigators to update the registry and recognize our error in not requiring them to do so during peer review.Although the results are inconclusive and the trial conduct was imperfect, this study is one of very few randomized controlled trials evaluating the effectiveness of masking policies on clinical outcomes. The trial does not provide a simple yes or no answer to the question the investigators set out to answer, but we published it because it contributes important information beyond the laboratory and observational studies that the comments note. Comments0 CommentsSign In to Submit A Comment Luc Bherer MD, Michael Levy MPH, Kevin Hedges PhD, CIH, COH1. Public Health Direction of Nunavik 2. Environmental Health Specialist and Epidemiologist 3.Former president and current board member Workplace Health Without Borders WHWB International29 August 2023 Your answer perpetuates systemic gender bias and health disparities We concur with the authors that conducting a study involving healthcare workers (HCWs) with «no-mask control group» would have raised ethical concerns. Nevertheless, it raises another ethical dilemma from the absence of definitive answers regarding the superiority of respirators over medical masks (MMs) in safeguarding HCWs against inhaling bioaerosols potentially carrying highly infectious diseases. Is it justifiable, then, to undertake an epidemiological study that omits a crucial control group on the grounds that "masking was the established norm during the trial period"? Asserting that this study deserves publication despite its limitations and vulnerabilities is a flawed perspective. Furthermore, the long-standing advocacy by Loeb for the concept of non-inferiority between MMs and respirators is inherently problematic. This study compares two devices designed for distinct purposes. MMs primarily shield others by capturing larger droplets emitted by the wearer, while respirators are primarily crafted to protect the wearer from inhaling smaller particulates. In essence, can the tool of epidemiology be employed without a comprehensive acknowledgment of its constraints? Does the notion of non-inferiority hold merit when advocating for a device that offers only 66% protection compared to 83% against potent contagious ailments(1)? Have the significant repercussions stemming from the editorial decision to circulate a study perpetuating confusion regarding respiratory personal protective equipment—the final line of defense in prevention, and most susceptible to breaches against inhalation exposure—been duly contemplated? We are of the opinion that this limited perspective inadvertently perpetuates systemic gender bias and health disparities. Notably, the healthcare sector predominantly comprises female workers. In scenarios where male majority sectors address risks like inhalation of silica or asbestos, with diseases occurrence over decades, the preventative approach does not involve recommending MMs; rather, the emphasis is on the device offering the strongest theoretical respiratory protection. The misuse of epidemiology and disregard for aerosol physics and other scientific domains suggest a lack of comprehension concerning the intricate demands of occupational hazard management with respect to the precautionary principle which is one of the cornerstones of public health. Ignoring international respiratory protection standards such as CSA Z-94.4 possibly indicates a concerning lack of awareness about the potential adverse effects on HCWs' health resulting from the editorial decision to uphold this publication. Bottom line, for women majority in sectors of activity that offers care, such as health care and also schools and daycare, our answer is that non-inferiority is irrelevant and the best protection a necessity. References: 1. Andrejko KL, Pry JM, Myers JF, et al. Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection — California, February–December 2021.MMWR Morb Mortal Wkly Rep 2022;71:212–216.DOI: http://dx.doi.org/10.15585/mmwr.mm7106e1 The EditorsAmerican College of Physicians31 August 2023 Editor response to Bherer As we understand it, Drs. Bherer, Levy, and Hedges argue that because respirators have been accepted as the best protection against inhaling non-infectious particulates in industry, they should be assumed to protect against infectious aerosols in health care settings. This seems a spurious argument against conducting a randomized controlled trial that examines the actual question of interest as Loeb and colleagues did. The accusation that Annals' decision to publish this trial perpetuates gender bias and health disparities appears misplaced since trials should include a population that represents those most relevant for the condition being studied. Disclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L23-0074 Author, Article, and Disclosure InformationAuthors: Christine Laine, MD, MPH; Christina C. Wee, MD, MPH; Stephanie Chang, MD, MPH; Deborah Cotton, MD, MPH, MA; Vineet Chopra, MBBS, MD, MSc; Sankey V. Williams, MD; Yu-Xiao Yang, MD, MSCE; Eliseo Guallar, MD, MPH, DrPH; Eric A. Ross, PhDAffiliations: Editor in Chief, Annals of Internal Medicine Senior Deputy Editor, Annals of Internal Medicine Deputy Editor, Annals of Internal Medicine Deputy Editor, Statistics, Annals of Internal Medicine Associate Editor, Statistics, Annals of Internal Medicine Disclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L23-0074. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetailsSee AlsoMedical Masks Versus N95 Respirators for Preventing COVID-19 Among Health Care Workers Mark Loeb , Amy Bartholomew , Madiha Hashmi , Wadea Tarhuni , Mohamed Hassany , Ilan Youngster , Ranjani Somayaji , Oscar Larios , Joseph Kim , Bayan Missaghi , Joseph V. Vayalumkal , Dominik Mertz , Zain Chagla , Maureen Cividino , Karim Ali , Sarah Mansour , Lana A. Castellucci , Charles Frenette , Leighanne Parkes , Mark Downing , Matthew Muller , Verne Glavin , Jennifer Newton , Ravi Hookoom , Jerome A. 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Brosseau Metrics July 2023Volume 176, Issue 7KeywordsCOVID-19Health care providersInfectious diseasesPreventive medicine ePublished: 18 July 2023 Issue Published: July 2023 Copyright & PermissionsCopyright © 2023 by American College of Physicians. All Rights Reserved.PDF downloadLoading ...